JACK Straw emerged as a potential surprise runner to be Labour's next deputy leader today as questions continued over John Prescott's future.

The former Foreign Secretary - switched to Commons Leader in the reshuffle - was widely reported to be privately keen to run for the post.

And he was also said to have the backing of both Tony Blair and Gordon Brown in any bid - with Downing Street sources reportedly dubbing him the natural choice.

Education Secretary Alan Johnson sparked fresh speculation over the beleaguered Deputy PM's future by publicly admitting a desire for the role in a TV interview.

And with Northern Ireland Secretary Peter Hain and Justice Minister Harriet Harman also expected to run, the possible field was growing.

Revelations

Mr Prescott's position has been under intense scrutiny since being stripped of his department in a reshuffle following revelations of his affair with a secretary.

Last week he gave up grace-and-favour country residence, Dorneywood, in a bid to quell dissent over his retention of his pay and perks.

And he has insisted he is not about to quit - telling MPs he would be in place to celebrate his 10th anniversary as Deputy PM in May 2007.

His determination to stay on is boosted today by a poll showing nearly two thirds of Labour activists do not want him out of office.

Poll

The YouGov survey for the Sunday Times found 56% thought Mr Prescott - on a tour of the US and Canada talking about climate change - should remain as Deputy PM for as long as Tony Blair was in 10 Downing Street.

Another 9% were keen to see him continue even longer with 25% preferring him to quit immediately - similar figures to opinions on his role as deputy leader.

And despite fears his reputation among Labour women had been damaged by his affair with diary secretary Tracey Temple, their rating was the same as for male activists.

Labour chairman Hazel Blears - also suggested as another possible successor today - urged Labour MPs yesterday to end "pointless" speculation over Mr Prescott's future.

She said there was "absolutely no vacancy" for a new Deputy Prime Minister despite claims that a battle for the leadership of the party had begun.

Interest

That suggestion was prompted by Education Secretary Alan Johnson, the first Cabinet minister to openly admit an interest in the job.

In an interview to be broadcast this morning, he told GMTV that while he would not campaign while Mr Prescott was in the job, it was a role he would like to take on.

His comments were seized on by backbencher Ian Davidson, who said it meant "the starting gun in the leadership and deputy leadership election has already been fired".

Mr Prescott - after addressing a conference on urban renewal in the US last night - will travel to Canada today for further meetings.

On Tuesday he will meet members of the new Canadian government.